Performance of a Coupled Arctic Climate Model Compared to MOSAiC Observations and its Sensitivity to a Change in Snow Thermal Conductivity

Climate models like the coupled Arctic atmosphere-ocean-sea ice model HIRHAM-NAOSIM are helpful to gain a deeper understanding of Arctic Amplification and interactions between atmosphere, ocean and sea ice. HIRHAM-NAOSIM is evaluated in Arctic winter compared to data from the MOSAiC expedition for February 2020.
A warm surface temperature bias of more than 5°C during clear-sky conditions is discussed in terms of modeled surface energy budget, clouds and atmospheric stability. HIRHAM-NAOSIM's control run underestimates the stable atmospheric stratification and has a positive bias in liquid water path and longwave radiation during observed clear-sky time periods.
Though the positive longwave radiative bias outweighs the impact of a changed snow thermal conductivity and the positive temperature bias during radiatively clear state remains, a halved conductivity of 0.15 Wm^-1K^-1 reduces the simulated surface temperature by up to 5°C and causes a higher occurrence of stable atmospheric conditions.